1. Field of the Invention
The present invention concerns a line with bundle conductors for transmitting electric energy, to which there are associated metal or dielectric cables incorporating optic fibres for telecommunication.
2. Description of the Prior Art
In recent years, telecommunication systems using cables with optic fibres, associated to electric energy transmission systems, have been installed in various parts of the world. Most of the installations set up so far have been adopting, among the various possible solutions (ground cables and energy conductors incorporating optic cables, dielectric optic cables suspended or tied to the ground cable or to the conductors, or wound around the same, self-supported dielectric optic cables), that according to which the cable incorporating optic fibres is inserted into the ground cable of the electric line. In this case, the conventional ground cable--which, in a line for transmitting electric energy, is positioned above the conductors and is supported by the upper part of the towers or tops--is replaced by a thicker cable housing the cable incorporating optic fibres. The ground cable will thus perform both its traditional function of protecting the line against overvoltages due to atmospheric electricity, and the function of mechanical support for the optic fibres cable.
Said solution, though allowing on one hand to promptly install telecommunication lines with satisfactory performances, presents on the other hand several inconveniences, among which the following are particularly evident:
the impossibilty to equip each electric line with more than two cables incorporating optic fibres;
the heavy weight of the ground cable associated to the optic fibres cable, which makes it indispensable--in case of installation on already existing electric lines--to introduce substantial structural modifications on the line itself;
the risk that the transmission parameters of the optic fibres may be altered due to overheating of the whole cable because of the passage of short circuit currents;
the sophisticated technology of construction and assembly of the joints, which makes them particularly uneconomic.
These inconveniences reduce the overall economic advantages which could derive from associating telecommunication systems using optic fibres to the already existing electric lines.